Method of making tear-resistant adhesive/combination bond pattern

ABSTRACT

Bonded composites, absorbent articles comprising such bonded composites, and processes for bonding thin-section elements. The bonded composite has first and second thin-section elements bonded to each other, at least in part by bond elements and at least in part by adherent material. The adherent material is disposed between the first and second thin-section elements proximate and about the bond elements. The adherent material, at least in part, bonds the thin-section elements to each other at loci of the adherent material. The bond patterns are arranged and configured to preferentially direct stresses imposed on the bond pattern, inwardly into the interior of the bond pattern for distribution, dissipation, and termination.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional application claiming priority under 35U.S.C. 120 to application Ser. No. 09/944,242 filed Aug. 30, 2001, nowU.S. Pat. No. 6,652,501, which is incorporated herein by reference inits entirety, which claims priority to provisional application Ser. No.60/229,189, filed Aug. 30, 2000.

BACKGROUND

The present invention relates to a bonded composite of a firstthin-section element of sheet material and a second thin-section elementbonded together by a bond pattern. More particularly, one of thecontemplated applications for the present invention is in bonding outercover and body side liner thin-section elements of absorbent articles toone another.

Absorbent articles have been known for a long time as personal carehygiene products. Absorbent articles find use, for example, as diapers,training pants, incontinence products, women's sanitary pads, and thelike. Such absorbent articles are designed and constructed to absorb andstore liquid bodily excretions such as urine, menstrual fluid, or blood.Women's sanitary pads are used, for example, to absorb the liquidsexcreted prior to, during, and after menstruation.

In absorbent articles, the portions of the article where differentlayers or components are bonded to each other tend to incur significantstress concentrations, and in absorbent articles using conventional bondpatterns, tend to fracture at those bonded locations under suchstresses. In conventional patterns used in absorbent articles, bondlocations are disposed in uniform and crossing straight lines andstraight rows of circular bond elements. The inventors herein have notedthat such bond configuration has been found to enhance the probabilitythat the absorbent article will tear and that the tear propagates alongthe side edge of the bond pattern. Tearing properties of suchconventional patterns can be compared to perforated paper forms.

The problem addressed in the present invention is thus to provide abonded composite demonstrating a bond pattern, and an absorbent articleimplementing the bond pattern, whereby the configuration of the bondpattern discourages the possibility for fracture of the bonded compositeor absorbent article at the bond pattern.

The present invention solves this problem by means of the bondedcomposite as well as the absorbent article both disclosed and describedin the independent claims. Additional advantageous embodiments of theabsorbent article in accord with the invention and of the process inaccordance with the invention arise from the dependent claims, thespecification, and the drawings.

It is an object of this invention to reduce the ease of tearing of abonded composite or absorbent article by introducing bonding patternswhich discourage straight fracture of the bonded materials, andencourage dissipating an initially concentrated force within asubstantial area of the bonding pattern.

SUMMARY

In a first family of embodiments, the invention comprehends a bondedcomposite. The bonded composite comprises, as a first thin-sectionelement, a first layer of sheet material, a second thin-section elementbonded, to the first thin-section element, at least in part by bondelements, and at least in part by adherent material. The adherentmaterial is disposed between the first and second thin-section elementsproximate and about ones of the bond elements. The adherent material, atleast in part, bonds the thin-section elements to each other at loci ofthe adherent material. The combination of the adherent material and thebond elements defines a bond pattern.

The bond pattern has a pattern length, a pattern width represented byfirst and second side edges of the bond pattern, and a centrallongitudinal axis, typically centered on the bond elements. The sideedges of the bond pattern and a corresponding pattern area between suchside edges are defined generally by those areas of the respectivethin-section elements which participate in absorbing and dissipating, byoperation of the bond pattern, stresses received into the bond patternfrom external sources.

The bond pattern has a pattern density defined generally by the fractionof the pattern area occupied by the bond elements. The bond elementsproximate the side edges are spaced farther apart from each other thanbond elements disposed more away from the side edges, thus creating arelatively less dense portion of the bond pattern proximate the sideedges of the pattern, as measured by bond element fraction of thepattern area, and a relatively more dense portion of the bond pattern,as measured by bond element fraction of the pattern area, away from theside edges.

The bond pattern reflects application of force urging the first andsecond thin-section elements toward each other in face-to-facerelationship to form an array of separate, distinct, and spaced elongatebond elements affixing the first and second thin-section elements toeach other.

Bonds corresponding to the bond elements are activated by combinedapplication of adherent material, pressure, and one of thermal energy orultrasonic-frequency energy to at least one of the first and secondthin-section elements.

In some embodiments, the bond pattern comprises, as ones of the bondelements, a first sub-array of longitudinally-oriented separate,distinct, and spaced stress receptor elements disposed along the length,and proximate the side edges of, the bond pattern. In such embodiments,the bond pattern can also comprise, as ones of the bond elements, asecond sub-array of longitudinally-oriented separate, distinct, andspaced transfer and dissipation elements spaced along the length of thebond pattern, typically inwardly of the side edges of the bond patternand generally inwardly of the stress receptor elements. Respective onesof the transfer and dissipation elements can have first ends disposedtoward an interior of the bond pattern. The respective transfer anddissipation elements can extend to second ends adjacent the side edgesof the bond pattern between respective ones of the stress receptorelements. The stress transfer and dissipation elements can directstresses inwardly into the interior of the bond pattern, and candissipate such stresses on the interior of the bond pattern.

In preferred embodiments, the adherent material comprises adhesiveselected from the group consisting of contact adhesives, pressuresensitive adhesives, hot melt adhesives, two-part chemically activatedadhesives, and mixtures and blends of such adherent materials.

The adherent material can be distributed and/or dispersed between thefirst and second thin-section elements as a result of the force beingapplied to the thin-section elements, such distribution and/or dispersalof the adherent material assisting in defining outer transverse edges ofthe adherent material in the bond pattern.

In preferred embodiments, at least one of the first thin-section elementand the second thin-section element comprises polymeric materialselected from the group consisting of polyolefins includingpolyethylenes and polypropylenes, polyesters, and polyamides, andcopolymers, mixtures, and blends of such polymeric materials.

Generally, at least one of the first thin-section element and the secondthin-section element comprises a fibrous web defining a multiplicity ofrandomly-spaced small openings extending from a major surface of the webinto the interior of the web.

In some embodiments, the bond elements define the bond pattern in arepeating arrangement of pattern segments.

In some embodiments, outer edges of the adherent material define anadherent material pattern corresponding with at least about 50 percentof the pattern area of the bond pattern, preferably, with at least about75 percent of the pattern area of the bond pattern, more preferably,with substantially all of the pattern area of the bond pattern.

In a second family of embodiments, the invention comprehends a bondpattern, reflecting application of force, which urges the first andsecond thin-section elements toward each other in face-to-facerelationship to form an array of separate, distinct, and spaced elongatebond elements affixing the first and second thin-section elements toeach other. Bonds corresponding to the bond elements are activated by acombined application of adherent material, pressure, and one of thermalenergy or ultrasonic-frequency energy to at least one of the first andsecond thin-section elements. The adherent material is one or bothdistributed and dispersed between the first and second thin-sectionelements as a result of the force being applied to the thin-sectionelements. One or both of the distribution and dispersal of the adherentmaterial assist in defining outer transverse edges of the adherentmaterial in the bond pattern.

As ones of the bond elements, a first sub-array oflongitudinally-oriented separate, distinct, and spaced stress receptorelements is disposed along the length, and proximate the side edges of,the bond pattern. A second sub-array of longitudinally-orientedseparate, distinct, and spaced transfer and dissipation elements isspaced along the length of the bond pattern, preferably inwardly of theside edges of the bond pattern and preferably generally inwardly of thestress receptor elements. Respective transfer and dissipation elementshave first ends disposed toward an interior of the bond pattern, andwhich extend to second ends adjacent the side edges of the bond patternbetween respective ones of the stress receptor elements. The stresstransfer and dissipation elements direct stresses inwardly into theinterior of the bond pattern, and assist in dissipating such stresses onthe interior of the bond pattern.

In a third family of embodiments, the invention comprehends as ones ofthe bond elements, a first sub-array of longitudinally-oriented separateand distinct stress receptor elements disposed proximate the side edgesof the bond pattern, and spaced at first distances from each other alongthe length of the bond pattern, and a second sub-array oflongitudinally-oriented separate and distinct transfer and dissipationelements preferably disposed inwardly of the side edges and preferablyinwardly of the stress receptor elements, and at second distances fromthe stress receptor elements less than the spacing of respective ones ofthe stress receptor elements from each other.

In some embodiments, respective transfer and dissipation elements havefirst ends disposed toward an interior portion of the bond pattern, andextending to second ends adjacent the side edges of the bond patternbetween respective ones of the stress receptor elements. In suchembodiments, the transfer and dissipation elements direct stressesinwardly to the interior portion of the bond pattern, and assist indissipating such stresses at the interior portion of the bond pattern.

In a fourth family of embodiments, the invention comprehends anabsorbent article having a front portion and a rear portion, and acrotch portion extending between the front portion and the rear portion.The absorbent article comprises, as a first thin-section element, afirst layer of sheet material, and a second thin-section element bondedto the first thin-section element, at least in part, by bond elements.The absorbent article further comprises adherent material disposedbetween the first and second thin-section elements proximate and aboutones of the bond elements. The adherent material at least in part bondsthe thin-section elements to each other at loci of the adherentmaterial, the combination of the adherent material and the bond elementsdefining a bond pattern. The absorbent article also comprises anabsorbent core disposed adjacent at least one of the first thin-sectionelement and the second thin-section element.

In a fifth family of embodiments, the invention comprehends a processfor bonding a first thin-section element and a second thin-sectionelement to each other. The process comprises applying an adherentmaterial to at least one of the first and second thin-section elementsover at least part of an area of the respective thin-section materialwhich is to be bonded. The process further comprises bringing the firstand second thin-section elements together, including at the area to bebonded. Additionally, the process includes applying force urging thefirst and second thin-section elements toward and intosurface-to-surface contact with each other including at the area to bebonded, and applying at least one of thermal energy orultrasonic-frequency energy to at least one of the first and secondthin-section elements in the area to be bonded, thereby forming an arrayof elongate bond elements and activating the adherent material proximateand generally about ones of the bond elements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B, and 1C show plan views of representative bond patterns ofthis invention.

FIGS. 2A, 2B, 2C, 2D show plan views of representative bond patterns ofthis invention employing adherent material in addition to specific bondelements.

FIGS. 3A and 3B show enlarged representations of preferred relationshipsbetween respective elements of the bond patterns of FIGS. 1A and 1C,respectively.

FIGS. 4A and 4B each show, as a representative absorbent article, a pairof training pants illustrating use of the bond patterns of FIGS. 1A and1C, respectively, along the side seams.

FIG. 5 shows, as another representative absorbent article, a diaperillustrating use of the bond pattern of FIG. 1C along the side seams aswell as to adhere the ears to the outer cover.

FIG. 6 shows a representative pictorial side elevation of a bonding nipsuch as can be used in continuous bonding processes employing bondpatterns of the invention.

FIG. 7 is a table showing composite contact lengths of the bond elementsacross the width of the bond pattern, at spaced locations along thelength of the bond pattern.

FIG. 8 shows a graph of the composite contact lengths of respectivespaced locations illustrated in the table of FIG. 7.

The invention is not limited in its application to the details ofconstruction or the arrangement of the components set forth in thefollowing description or illustrated in the drawings. The invention iscapable of other embodiments or of being practiced or carried out inother various ways. Also, it is to be understood that the terminologyand phraseology employed herein is for purpose of description andillustration and should not be regarded as limiting. Like referencenumerals are used to indicate like components.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

FIGS. 1A and 1B show preferable embodiments of bond pattern 10 of theinvention, which is described more fully in application Ser. No.09/651,042 filed Aug. 30, 2000, of common assignment herewith, and whichis herein incorporated by reference in its entirety. Bond pattern 10 hasa first side edge 16, a second side edge 18, and a central longitudinalaxis 20 which divides the bond pattern 10, as defined by the bondelements, into a first opposing pattern combination 22 on a first sideof axis 20 and a second opposing pattern combination 24 on an opposingsecond side of axis 20. Bond pattern 10 has a pattern length defined interms of distance measured along central longitudinal axis 20, and apattern width “W” represented by distance between first side edge 16 andsecond side edge 18 of bond pattern 10. Correspondingly, the overallarea of bond pattern 10 is defined as the area which participates inabsorbing and dissipating, by operation of bond pattern 10, stressesreceived into the bond pattern from external sources, the bond patternarea generally being defined within the confines of side edges 16 and18.

In product implementations of the invention, the bond pattern reflectsapplication of force which urges first and second thin-section e.g.sheet material elements toward each other in face-to-face relationshipto form, as repeating bond segments, an array of separate, distinct, andspaced elongate bond elements in a repeating arrangement affixing thefirst and second thin-section elements to each other. Ones of the bondelements extend width-wise across the bond pattern, from loci proximatethe side edges up to at least about the longitudinal axis, at angles “α”of between about 10 degrees and about 65 degrees, preferably about 15degrees to about 50 degrees, with respect to the longitudinal axis. Mostpreferred angles are about 25 degrees to about 40 degrees The anglesillustrated in the drawings represent about 30 degrees from thelongitudinal axis.

While legs 26 are shown in the drawings as being straight, the legs canbe curved in some embodiments. In such case, the respective angles “α”vary along the lengths of such legs in accord with the respectivecurvatures of the legs.

A bond width is defined by an end-to-end length corresponding to bondelements arrayed across the width of the pattern perpendicular to thelongitudinal axis, including spaces between respective ones of the bondelements, and spaces between bond elements and side edges 16, 18. A bondwidth can be measured at any point along the length of the bond pattern,and such bond width extends along the pattern width. The bond width thuscorresponds to the pattern width “W” at a given locus along the lengthof the bond pattern.

Bond element contact lengths at respective bond elements arecorrespondingly defined along the bond width. The additive combinationof the bond element contact lengths along a respective bond widthdefines the composite contact length along the respective bond width.The composite contact length, taken at equally spaced intervals along alength of the bond pattern, defines an average composite contact length.The composite contact length at a given point along the length of thepattern varies from the average composite contact length by no more thanabout 13 percent, preferably by no more than about 10 percent, and morepreferably by no more than about 8 percent.

In the illustrated embodiments, opposing pattern combinations 22 and 24are substantially the same and are employed as off-set mirror images ofeach other. Thus, pattern combinations 22, 24 are positioned along thelength of the pattern such that the opposing pattern combinations areasymmetric with respect to each other by expression of such offset.While the opposing patterns are asymmetric with respect to each other,both first opposing pattern combination 22 and second opposing patterncombination 24 are internally symmetric, as well as expressing repeatingsegments thereof along the length of bond pattern 10.

Bond pattern 10 is defined by a plurality of bond elements. In preferredembodiments, bond elements proximate side edges 16, 18 are spacedfarther apart from each other than bond elements which are disposed moreaway from the side edges, thus creating a pattern density which is lessdense at the side edges of the pattern than away from the side edges.

Bond pattern 10 preferably comprises regularly repeating bond segments,each repeating bond segment comprising a defined set of bond elementsspaced according to a generally fixed segment pattern. A plurality ofbond elements establishing repeated element combinations defines suchbond segment, although not all bond elements need be defined in bondsegments. Therefore, a similar bond pattern using one or more orphanbond elements which orphan elements do not repeat regularly, or whichelements are so far outside the rest of the bond pattern that such bondelements do not cooperatively participate with the other bond elementsin absorbing and dissipating, by operation of the bond pattern, stressesreceived into the bond pattern, is within the scope of the presentinvention.

The illustrated bond pattern comprises, as a first sub-array of the bondelements, longitudinally-oriented separate, distinct, and spaced stressreceptor elements 12 disposed at or near, namely proximate, first sideedge 16 and second side edge 18. Receptor elements 12 are typicallyevenly spaced along the length of bond pattern 10.

Stress transfer and dissipation elements 14 define a second sub-array oflongitudinally-oriented separate, distinct, and spaced bond patternelements, typically evenly spaced along the length of bond pattern 10,inwardly of the side edges of the bond pattern and typically inwardly ofstress receptor elements 12. Each respective transfer and dissipationelement has a first end 28 and a second end 29, and legs 26 extendingfrom the respective ends toward each other and outwardly of thelongitudinal axis, and meeting at an outwardly-disposed joinder locus 27of the legs 26 between stress receptor elements 12. Stress receptorelements 12 alternate along the length, and on opposing side edges, ofthe bond pattern. Stress transfer and dissipation elements 14 alternateon opposing-sides, and along the length, of bond pattern 10, generallybetween respective stress receptor elements. Stress transfer anddissipation elements 14 thereby provide the desired side-to-side balanceto the bond element width of bond pattern 10.

In general, then, preferred bond patterns comprise regularly repeatingbond segments, each repeating bond segment comprising at least onestress receptor element 12 and at least one stress transfer anddissipation element 14, the elements 12 and 14 being spaced according toa generally fixed segment pattern wherein each stress receptor element12 is balanced by a transfer and dissipation element, or a stresstermination element, or both, or other balancing element or elements, onthe opposing side of longitudinal axis 20.

In e.g. the embodiments illustrated in FIGS. 1A and/or 1B, an imaginaryline 80, shown in FIG. 3A, along a given bond width at a given locusalong the length of the bond pattern traverses a stress receptor element12 on a first side of longitudinal axis 20 and a respective leg 26 ofthe corresponding transfer and dissipation element 14 on the opposingside of the axis. The distance between distal ends of the most remoteones of the bond elements along a respective imaginary line spanning thewidth of the bond pattern, so defined and illustrated in FIG. 3A,represents at least about 70 percent, up to 100 percent, of the width ofthe bond pattern, more preferably, at least about 75 percent up to about90 percent, of the width of the bond pattern, and even more preferablyat least about 80 percent up to about 85 percent, of the width of thebond pattern.

The distance between the ends of the composite contact length isillustrated as less than 100 percent of the width of the bond pattern,wherein the transfer and dissipation elements are located inwardly ofside edges 16, 18. In some embodiments, the outer portions 82 of thetransfer and dissipation elements can be disposed at side edges 16, 18,whereby the composite contact length can be as great as 100 percent ofthe width of the bond pattern at the given locus along the length of theweb.

Thus, outwardly-disposed portions of respective legs 26 of the transferand dissipation elements provide balancing support on opposing sides ofthe longitudinal axis balancing e.g. respective stress receptor elements12 during formation of the bond pattern 10.

Because transfer and dissipation elements 14 extend both directionsalong the length of the bond pattern, elements 14 can transfer, to theinterior of the bond pattern, stresses coming from either directionalong the length of the bond pattern. Similarly, angles “α” of thetransfer and dissipation elements 14 tend to promote the transfer ofstresses to the interior of the bond pattern, and are effective totransfer stresses entering the bond pattern from any direction inwardlyfrom the side edges and toward the interior of the bond pattern.Additionally, because of the similarity of the opposing patterncombinations located on opposing sides of central longitudinal axis 20,the bond pattern effectively balances nip force exerted on one side ofthe pattern with a balancing nip force on the opposing side of the bondpattern, while the bonds are being formed.

In an embodiment illustrated by FIG. 1B, and starting with the structureof FIG. 1A, portions of the transfer and dissipation elements where thelegs join at 27 in FIG. 1A have been excised and moved to locations ator near central longitudinal axis 20 and on the same side of the patternas the respective donor transfer and dissipation element, thus toprovide respective stress termination elements 13. Stress terminationelements 13 tend to coordinate degeneration, dissipation, and preferablytermination, of stresses transferred into the interior portion of thebond pattern adjacent axis 20.

The resilience of materials known for use in e.g. the body side liner orthe outer cover of absorbent articles, in combination with controlledpattern density, enables the bond pattern to direct inwardly toward thelongitudinal axis a wide variety of forces imposed on the bond patternfrom any direction along the length or width of the bond pattern. Bydirecting, transferring, and distributing stresses toward the interiorof the bond pattern, the invention relieves the side edges of the bondpattern from bearing a corresponding portion of the stress which istypically borne by side edge portions of the bond pattern. Thus, thestress born by the respective side edge when a given force is imposed onthe bond pattern, is less for bond patterns of the invention than for aconventional bond pattern having a symmetrically arrayed square patternof lines and rows of circular bond elements. Accordingly, bond patternsof the invention can tolerate more overall stress than such conventionalbond patterns. Thus, not only does the bond pattern reduce thestraight-line, perforation-like failure tendency of conventionallinearly-arranged bond patterns, but the invention is correspondinglycapable of tolerating and distributing greater levels of stress than aconventional bonding pattern.

Bond pattern 10 can be used to unite sheets of material along theentirety of the length of the material, or as in the case of theexamples cited, along a portion of the length or width of a personalcare absorbent article. Bond pattern 10 can also be used to uniteintermittent portions of respective work pieces in a particularconfiguration e.g. defined in terms of length and/or width. Bond pattern10 can further be used to unite portions of work pieces according tomore than one configuration. Bond pattern 10 can yet further be used tounite materials along a defined length of web material. In all suchimplementations, bond pattern 10 can be used to bond a relativelysmaller element or work piece to a relatively larger element or workpiece. Examples of use of the bond pattern in an absorbent articleinclude, but are not limited to, bonding a fastening ear to the outercover, bonding a leg flap to the outer cover or the body side liner,bonding containment flaps to the body side liner, and bonding a landingzone to the outer cover.

In yet another embodiment, bond pattern 10 comprises a pattern densitydefined generally by the spacing and number of bond elements within adefined portion of the pattern area, wherein bond elements proximate theside edges are spaced farther apart from each other than bond elementswhich are disposed more away from the side edges, thus creating apattern density which is less dense at the side edges of the patternthan away from the side edges.

FIG. 1C shows a bond pattern 10 having a first side edge 16 and a secondside edge 18. A central longitudinal axis 20 divides the bond pattern 10into a first pattern combination 22 and a second opposing patterncombination 24. Bond pattern 10 has a pattern length defined generallyas the distance by which the pattern extends along the centrallongitudinal axis 20, and a pattern width “W” represented by thedistance between first side edge 16 and second side edge 18.Correspondingly, the overall area of the bond pattern is defined as thearea which participates in absorbing and dissipating, by operation ofthe bond pattern, stresses received into the bond pattern.

The embodiment of FIGS. 1C and 3B is more fully described in applicationSer. No. 09/651,041, filed Aug. 30, 2000, of common assignment herewith,and herein incorporated by reference in its entirety.

The portion of bond pattern 10 of FIG. 1C which is located betweencentral longitudinal axis 20 and first side edge 16 makes up a firstpattern combination 22. Correspondingly, the portion of bond pattern 10which is located between central longitudinal axis 20 and second sideedge 18 makes up a second opposing pattern combination 24. In theembodiment of FIG. 1C, first opposing pattern combination 22 and secondopposing pattern combination 24 represent substantially the samearrangement of bond elements and bond element relationships and areemployed as off-set mirror images of each other The first and secondopposing pattern combinations are positioned along the length of thepattern such that the opposing pattern combinations are asymmetric withrespect to each other. While the opposing patterns are asymmetric withrespect to each other, both pattern combination 22 and patterncombination 24 are internally symmetric, as well as being symmetric withrespect to the length of bond pattern 10.

In one embodiment, bond pattern 10 comprises a pattern density definedgenerally by the number and spacing of bond elements within a definedportion of the pattern area, wherein bond elements proximate the sideedges are spaced farther apart from each other than bond elements whichare disposed more away from the side edges, thus creating a patterndensity which is less dense at the side edges of the pattern than awayfrom the side edges.

In the illustrated embodiment of FIG. 1C, each of the opposing patterncombinations comprises stress receptor elements 12 proximate the sideedges of the bond pattern, transfer and dissipation elements 14 disposedinwardly of the stress receptor elements 12, and stress terminationelements 16 disposed inwardly of transfer and dissipation elements 14. Aplurality of such bond elements establishing repeated elementcombinations and spacial arrangements, along the length of the bondpattern, defines a repeat pattern.

Stress receptor elements 12 are shown in FIG. 1C, disposed proximateside edges 16 and 18, along the length of bond pattern 10 as a firstsub-array of longitudinally-oriented separate, distinct, and spaced bondelements. Transfer and dissipation elements 14 are shown as a secondsub-array of longitudinally-oriented separate, distinct, and spaced bondpattern elements spaced along the length of the bond pattern. Thetransfer and dissipation elements are disposed inwardly of the sideedges of the bond pattern and generally inwardly of the stress receptorelements 12. A third sub-array of longitudinally-oriented separate,distinct, and spaced stress termination elements 13 is disposedgenerally inwardly of the transfer and dissipation elements 14 onopposing sides of, and oriented generally along, central longitudinalaxis 20. In the illustrated embodiments, combinations of one stressreceptor element 12 and two stress transfer and dissipation elements 14alternate with each other along the length of the bond pattern on bothsides of the bond pattern, and thereby provide a side-to-side walkingadvance of element groupings along the length of the bond pattern. Bondpattern combinations 22 and 24 are thus longitudinally asymmetric withrespect to each other along the length of the bond pattern thereby todistribute the collective bond element widths relatively more evenlyalong the length of the bond pattern. Such distribution contributes toservice life of the rolls used in a rotary bonding nip.

A stress transfer and dissipation element 14 is further defined ashaving a first end 28 and a second end 29. First end 28 of a transferand dissipation element 14 is disposed at an interior portion of thebond pattern relative to the second end 29. The second end 29 of atransfer and dissipation element 14 is located outwardly in the bondpattern adjacent a respective side edge of the bond pattern between andinwardly of a respective one of the stress receptor elements 12. Secondends 29 of transfer and dissipation elements 14 are also distinguishedfrom first ends 28 in that the second end of a respective element 14 hasa greater radius of curvature in plan view than first end 28 of the sameelement 14.

The several bond elements preferably occupy from about 10 percent toabout 40 percent of the overall bond area of the bond pattern. In a morepreferable application of bond pattern 10, the bond elements occupy fromabout 12 percent to about 30 percent of the overall bond area of thebond pattern. In an even more preferable application of bond pattern 10,the bond elements occupy from about 15 percent to about 25 percent ofthe overall bond area of the bond pattern. The specific preferredfraction varies from pattern to pattern, from process to process, andconsidering the material being bonded. If the bond element fraction istoo low, the elements are unable to cooperatively support each otherwhereby the stress may not be adequately attenuated in the bond patternand whereby a lack of minimum bond element density may result in layersof a bonded composite disassociating with one another. If the elementfraction is too high, areas of the web between bond elements are notsufficiently extensive to enable unbonded areas of the web material, inthe bond pattern area, to effectively distribute the stresses amongadjacent bond elements, or to dissipate the stresses internally withine.g. unbonded portions of the bond pattern.

In some embodiments of the present invention, bond pattern 10 can beused to unite sheets of material along the entirety of the length of thematerial, or in the case of the examples illustrated herein, along theentirety of the length or width of an absorbent article.

In another family of embodiments of the present invention, bond pattern10 can be used to unite intermittent segments of a defined length of thee.g. absorbent article.

In yet another family of embodiments of the present invention, bondpattern 10 can be used to unite variable-width segments of a length ofthe e.g. absorbent article.

In still another family of embodiments of the present invention, bondpattern 10 can be used to unite materials along a defined length of thematerials being bonded. In all of the embodiments, bond pattern 10 canbe used to bond smaller elements such as separate and distinct workpieces to a larger element such as a generally endless web.

Bond elements 12, 13, 14 have been described in terms of bonds formed byemploying ultrasonic energy, thermal energy, and the like, incombination with pressure at a nip Other methods of forming suchseparate, distinct, and discrete bonds will be known to those skilled inthe bonding art.

In this invention, adherent material, such as chemical adhesivematerial, can be used in forming the bond pattern, in combination withsuch bond elements. Such adherent material is preferably employed withinthe bond pattern as defined by the bond elements 12, 13, 14, and mayextend outwardly or inwardly from the width of the bond pattern asdefined by the bond elements. Such adherent material can be applied toone or both of the thin-section materials which are being bonded to eachother. The methods which can be used for applying such adherent materialto the thin-section elements are as varied as the methods conventionallyknown for applying adherent compositions to materials to be bonded toeach other. Thus, typical methods of applying the adherent materialinclude spraying from nozzles, coating from a coating roll, transferroll coating, dip applications, wire rod spreaders, and the like.

The adhesives contemplated as being most commonly used in this inventionare liquid adhesives, or are activated such as by melting prior to-beingapplied to the thin-section materials being bonded to each other, thusto temporarily become liquid for purposes of being applied to thematerials being bonded; and after such application, such adherentmaterial may then revert to a solid or deformable plastic state.

After the fluid adhesive is applied to one or both of the thin-sectionsheet materials, the sheet materials are brought together typically withpressure, such as in a nip, to develop bonding contact which bonds thesheet materials to each other through the adhesive. Such nip, if shown,would be between adhesive applicator 70 and nip 60 in FIG. 6. The thusadhesively-bonded sheet materials then pass through nip 60 where bondelements 12, 13, 14 ane the like are developed.

Given that the adhesive is typically liquid, or at least flowable, whenbeing applied to the thin-section sheet material, the flowable/fluidadhesive is mobile, namely is susceptible to being moved about by forcesexerted on such adhesive, while in the liquid, flowable, fluid state. Aresult of such fluidity of the adhesive, when being used in such bondingoperation, is that the force used to develop the adhesive bonds, as wellas the force used to develop the separate bond elements, e.g. 12, 13,14, correspondingly develop fluid pressure on the liquid adhesive as theadhesive passes through a corresponding nip. Such fluid pressure e.g. atnip 60 or an earlier nip causes flow of such fluid adhesive to areas oflower fluid pressure. Such areas of lower fluid pressure existtransversely as well as longitudinally along the length of the bondpattern, from nip 60. While longitudinal movement of the adhesiverelieves the pressure temporarily, the moved adhesive re-enters therespective nip as the substrate continues to advance through the nip.Accordingly, permanent relief of the fluid pressure on particularelements of the fluid adhesive is achieved through movement of theadhesive transversely across the width of the nip/bond pattern, wherebythe moved adhesive traverses through the nip and out the downstream sideof the nip. Such transverse movement of the adhesive can result in anexpansion of width of that portion of the bond pattern which is definedin terms of adherent material such that such movement of adhesiveeffectively defines one or both outer edges of the adherent materialportion of the bond pattern.

The overall result, of using a bond pattern of bonding elements incombination with the adherent material around some or all of the bondingelements, is a synergy of cooperative distribution, dissipation, andtermination of stresses imposed on the bond pattern. The pattern ofadherent material in the combination especially promotes use ofcorresponding areas of both layers for stress distribution, for energyabsorption, and for discouraging fracture of sheet material at the bondpattern.

Because of such mobility of the adhesive, it is important that the widthof the pattern of adhesive which is laid down, and the density ofadhesive material to be laid down, in combination with the amount ofpressure applied at the bonding nip, the density and spacing of bondelements created at the nip, and the uniformity of pressure applied tothe elements being bonded at the nip, all be considered in arriving attarget width and target location for applying the adhesive.

The adhesive passes through the nip after being applied to the materialto be bonded (e g, a substrate/web), and while the adhesive is stillmobile. Accordingly, the pressure exerted at the nip causes the adhesiveto move especially transversely in the substrate or web therebypotentially changing the width of the adhesive pattern. Once theadhesive reverts to an immobile form, e.g. downstream of the bondingnip, the resulting width is stabilized. Such stabilized width isrepresented in FIGS. 2A, 2B, 2C, and 2D by the dashed lines at opposingsides of the respective FIGURES.

Referring first to FIG. 2A, first side edge 16 of adhesive pattern 11 isgenerally coincident with the outer extremities of pattern 10 of bondelements. FIG. 2A illustrates at first side edge 16 a more wavy lineindicating the uneven-ness which may attend transverse movement ofadhesive material as a result of the pressure at the nip. The secondside edge 18 in FIG. 2A is substantially straight, more representativeof a side edge not so affected by movement of the adhesive in thebonding nip.

FIG. 2B illustrates the embodiments wherein adhesive pattern 11, andthus side edges 16, 18 of the bond pattern, can extend outwardly on bothsides of bond pattern 10 from that potion of the bond patternrepresented by the bond elements.

FIG. 2C illustrates preferred embodiments wherein, on a lower side ofbond pattern 10, adhesive pattern 11 is coincident with second side edge18 of bond pattern 10, as defined by the bond elements, and on theopposing side of bond pattern 10, the adhesive extends somewhatoutwardly from the bond elements to form a wavy side edge 16 outsidethat portion of the width of the bond pattern which is represented bythe bond elements.

Having the adhesive extend outwardly from that portion of the width ofthe bond pattern which is represented by the bond elements providesplural benefits. First, the adhesive provides an advance area first lineof stress relief, such that the adhesive receives and distributes thestress to both thin-section elements before the stress reaches any ofthe bond elements.

Second, where the adhesive is generally consistently distributedthroughout the general area of its coverage, the adhesive provides for acontinuum of stress distribution to both thin-section web elementsthroughout the full bonded area of the substrates or sheet material,affected by the stress, as opposed to only the discrete areas defined bythe bond elements, or only a single one of the sheet material elements,whereby uniformity of stress distribution in the thin-section elementsis enhanced, which typically results in enhanced dissipation andtermination of stresses.

FIG. 2D illustrates embodiments wherein the outer edges of adhesivepattern 11 are disposed inwardly from side edges 16, 18 as defined bythe bond elements. Such inward disposition of the adhesive at theinterior of a bond pattern which is configured to transfer the stressesinto the interior of the bond pattern focuses the strength of theadhesive material in the bond pattern at locations of the bond patternwhere the adhesive material can provide the greatest effectiveness.Namely, the strength of the adhesive is focused on the areas of greatestneed for dissipation of stress, while leaving to the bond elements thetasks of receiving and directing the stresses toward the interior of thebond pattern.

In general, the benefit of the adhesive pattern inside the side edgeswhere the side edges are defined by the bond elements, is to improvedistribution of the stresses throughout the areas of the thin-sectionelements which are susceptible to being affected by the bond pattern. Inthat regard, the bond pattern is defined as the composite of the bondelements, and the adherent material, to the extend the adherent materialworks in combination with the bond elements in controlling stressreception, distribution, transfer, dissipation, and termination.

Where the adhesive pattern at least reaches, from inwardly of the sideedges as defined by the bond elements, to the side edges, adhesivebetween e.g. stress receptor elements tends to initiate the stressreception response, between the stress receptor elements, at the dashedline representing the edge of the adhesive material. Without thepresence of the adhesive material, initiation of response to stress atsuch location requires traverse of the stress either to an adjacent butdisplaced stress receptor element or to an adjacent but displacedtransfer and dissipation element. In either case of absence of adhesivematerial at edge 16 or 18, response to the stress is transferred fromthe local area where the stress crosses the side edge of the bondpattern as defined by the straight line connecting the stress receptorelements, whereby the stress reception response is somewhat lesseffective.

Typical adhesive patterns of the invention generally at least direct astress inwardly into the bond pattern. The adhesive patterns typicallyare continuous along at least a portion of the width of the bondpattern, and typically interact with the bond elements to the extent ofsharing distribution and dissipation of the stresses imposed on the bondelements. Typically, the adhesive pattern extends to some degree on bothsides of longitudinal axis 20, and is typically generally centered alongaxis 20, as illustrated in FIGS. 2A, 2B, 2C, 2D.

Within the width defined by the adherent material pattern, the adherentmaterial is typically continuous along such width, and such width istypically constant, or generally constant within manufacturingcapability to maintain such consistent width. The width variations shownin the drawings are exaggerations for illustration purposes of thevariations which are typically encountered in commercialimplementations. However, such variations are not generally preferred,and engineering work may be employed to attenuate such variations.

While the side edges can be defined functionally by those areas of therespective thin-section elements which participate in absorbing anddissipating, by operation of the bond pattern, stresses received intothe bond pattern from external sources, the side edges can also bedefined structurally. Namely, peripheral portions of those areas of therespective thin-section elements which participate in absorbing anddissipating the stress can constitute the side edges of the pattern. Theperipheral portions of such areas at particular loci can be defined asthose bonded areas which are furthest disposed from the centrallongitudinal axis and are disposed outwardly of ones of the bondelements, e.g. the stress receptor elements at the particular loci.

FIG. 3A shows an enlarged view of the bond pattern illustrated in FIG.1A. FIG. 3A includes imaginary connection lines 80 spaced evenly alongthe length of bond pattern 10, to help illustrate the relationshipsbetween the respective bond elements and the cooperative effect of suchspacial relationships as the positioning of the respective bond elementsworks to increase the wear life of both lower-disposed e.g. anvil roll62B (FIG. 6) and upper-disposed roll 62A.

FIG. 3A represents a single repetition of the bond pattern illustratedin multiple repetitions in FIG. 1A. In FIG. 3A, the several bondelements are shown divided by equally spaced imaginary increment lines84 which extend perpendicular to longitudinal axis 20, and parallel tolines 80. In FIG. 3A, each fifth line 84 is aligned with one of thelines 80. Thus, each fifth line 84 represents incremental portions ofthe length of a corresponding one of imaginary lines 80.

Lines 80 are used as convenient tools for indexing and evaluating thesignificance of lines 84. The spacing between respective lines 84, andthe frequency of lines 80, can be selected as convenient for the user'sanalysis. In the illustrated embodiment, the distances between adjacentimaginary increment lines 84 are approximately 0.008 inch. Suchdistances are preferably uniform along the length of the pattern beingevaluated. The length of the imaginary increment lines 84 generallyrepresents at least the width “W” of the bond pattern. Each suchdistance defines one of the five increments used in defining acorresponding imaginary line 80. The illustrated bond pattern isdesigned to keep the composite contact length, which is indicative ofthe sum of the lengths of respective line segments of any one line 84defined by each respective bond element crossed by any one line 84,including all sections thereof, within 0.010 inch of the averagecomposite contact length. The illustrated pattern is also designed sothat those projections or lands which are collective in forming the niphave combined widths which define the composite contact length, andwhich are relatively consistent as measured along successive adjacentlines 84, over the full length of the segment, and wherein successivesegments are both internally consistent within themselves, and areconsistent with respect to each other.

One of the primary benefits of embodiments of the invention illustratedin FIGS. 1A and 1B is attenuation of power feedback spikes in ultrasonicbonding embodiments of the invention. Such feedback spikes occur as aresult of characteristics of conventional bond patterns on e.g. a rotaryanvil. Power tends to be a function of rotation of the rotary anvil,e.g. 62B, combined with forces emitted from one or both of the horn andanvil. The emitted forces can be any of forces selected from the groupconsisting of pressure, ultrasonic energy, and thermal energy as appliedover time. Increases and decreases in power distribution across thewidth of a bond pattern can be defined by variations in compositecontact lengths as compared to the average composite contact length fora given bond pattern for at least a complete circumferential rotation ofan anvil.

Conventional bond patterns tend to demonstrate a wide variation incomposite contact lengths as compared to respective average compositecontact lengths. A given proportional variation in composite contactlengths causes the same proportional variation in power distribution fora conventional bond pattern. The variation is typically attendant e.g.bond patterns being created in a straight, linear-type arrangement ofcircular bonding elements. Embodiments of FIGS. 1A, 1B of the inventionpreferably demonstrate a variation in composite contact length of nomore than about 13% from the average composite contact length as therespective anvil makes a complete rotation. The consistency in powerdistribution of the such embodiments demonstrated by the lack ofvariance from the average composite contact length can also beindicative of consistency of resistence between the horn and anvil, ascontact area in the nip is a function of the respective compositecontact lengths. Thus, reduction in variation of respective compositecontact lengths from the average composite contact length, as in someembodiments of the invention, results in a steady power distributionacross the width of the bond pattern, and attenuation or avoidance ofpower spike feedback.

In addition, the side-to-side balance of the pattern and the consistencyof the composite contact length provide two further benefits. First,bending stress is attenuated on shafts supporting rolls 62A, 62B.Second, where roll 62B is the patterned roll, side-to-side surface wearon especially roll 62A is relatively more uniform, providing longer rolllife than patterns not exhibiting such consistency of composite contactlength.

Referring to FIG. 3A, the composite contact length is defined as the sumof the line lengths along the widths of the bond elements traversed by agiven imaginary increment line 84 between side edges 16 and 18. In theillustrated embodiment, imaginary increment lines are typically about0.030 inch long on each respective bond element, and the overall patternwidth “W” is about 0.38 inch. In such illustrated environment, variationin the composite contact length should be within 0.010 inch of theaverage composite contact length of such segments.

Referring to FIG. 3A, an important value in bond patterns of theinvention is that, during formation of the bond elements in the websand/or work pieces, the loci of bonding contact in the nip can beconsistently represented by bond elements on both sides of longitudinalaxis 20. For example, at any time during which a stress receptor element12 is receiving pressure in the nip, a transfer and dissipation element14 on the opposing side of axis 20 is also receiving pressure in thenip. Thus, any force on a supporting roll shaft arising from receptorelement 12 is countered by a second force, on the working face of theroll, arising from the opposing transfer and dissipation element 14, andtending to balance the first force. FIGS. 7 and 8 illustrate suchanalyses for each of the 60 line combinations 84 represented in FIG. 3A.

In addition to the reduction in shaft stress, such balanced pattern onthe anvil roll provides for balanced wear across the width of theworking surface of roll 62A. Such improved wear is especially valuablein an ultrasonic horn 62A which is used when the bonds are formed usingan ultrasonic bonding process. Indeed, the improved surface wearbenefits are more apparent where rolls 62A, 62B have different basediameters. In ultrasonic bonding processes, anvil roll 62B typically isdesigned to have a diameter different from that of the ultrasonic hornso as to not unacceptably attenuate resonance of the horn. Additionally,an anvil having a different diameter avoids wear associated withrespective surface portions of the horn repeatedly interacting withcorresponding surface portions of the anvil.

To that end, the pattern of some preferred embodiments can be suitablybalanced, side to side, where the distance between distal ends of themost remote ones of the bond elements along a respective imaginary linespanning the width of the bond pattern so defined represents a width atleast 70 percent as great as the width “W” of the bond pattern at therespective segment. Preferred distance between distal ends is about 80percent to 85 percent of width “W.” The distance may be as great as 100percent where e.g. bond elements 14 extend to the side edges of the bondpattern. However, some such embodiments may be subject to stresstransfer along the length direction of the resultant bond, at the sideedges of the bond pattern, whereby the design of such bond patterns mustconsider how stresses can be assuredly transferred from the receivingbond elements, e.g. stress receptor elements 12, toward the interior ofthe bond pattern, and away from the side edge, as taught herein.

Referring to FIG. 3B, a stress vector 72 received at receptor element12A is transmitted from receptor element 12A at the loci of smallestradius on the side of the receptor element opposite the stress receivingside. Dashed lines 92 illustrate the paths along which the stresstraverses, away from receptor element 12A to transfer and dissipationelements 14A, 14B. The received stresses are similarly transmitted tothe opposing sides of elements 14A, 14B, and thence outwardly from thesmallest radius portions to element 14C and termination element 13A,thence to elements 12B and 12C. The above paths of transmission of theforce into and through the interior of the bond pattern are indicated aspaths 92 in FIG. 3B. The indicated paths are merely illustrative, andnot limiting, of the distribution of forces in bond patterns of theinvention. However, such illustration is instructive that bond patternsof the invention, given the angles “α” and the spacing between receptorelements 12, actively direct stresses into the interior of the bondpattern wherein a plurality of bond elements simultaneously absorbportions of the stress such that no one or two bond elements at the sideedge of the bond pattern bear the entire burden of the stressing force.In the example of force vector 72, the stress is illustrated as beingborne primarily by four bond elements 14A, 14B, 14C, and 13A, three ofwhich are larger in size than the receiving element 12A, and thus cantheoretically tolerate greater amounts of stress than can receptorelement 12A.

In summary, a bond pattern of the invention operates as a compilation ofvarious and differing functioning bond elements of the bond pattern,along with the support of adhesive material between the bond elements.The side edges, and thus the unit area, of the bond pattern are definedgenerally by those areas of the respective thin-section elements beingbonded which participate in absorbing and dissipating, by operation ofthe bond pattern, stresses received into the bond pattern.

As stress is applied to a bonded composite or absorbent articledemonstrating a bond pattern of the invention illustrated in thedrawings, stress is initially received at the side edge of the bondpattern by an edge bond element such as a stress receptor element 12 andsubstantial portions of the received stress are typically transferred tothe next closest bond element, namely one or more of the transfer anddissipation elements. By designing the bond pattern so that the nextclosest bond element is located inwardly on the bond pattern,substantial portions of the stress are transferred inwardly of the bondpattern and away from the respective side edge, whereby the amount ofstress dissipated, absorbed at the side edge is lessened by the amountof stress which is transferred inwardly into the bond pattern. Bydisposing elements 14 at angle “α” with the longitudinal axis, thestress travels inwardly not only in being transferred from bond elementto bond element, but also in traveling along the length of bond elements14 toward the inner ends of such elements.

To the extent the resultant stress is reduced at the side edge, bytransfer inwardly from the side edge, the side edge may have unusedstress-accepting capacity, whereby the bond patterns of the inventionhave increased stress-bearing capacity compared to otherwise similar andconventional bond patterns.

The increased stress-bearing capacity of bond patterns of the inventionis attributable to the cooperative relationships among the respectivebond elements, as well as the structures and orientations of therespective bond elements. Stress receptor elements 12 initially receivestresses and relay the stresses inwardly to the next closest bondelement in the pattern, for example an element 14. Stress transfer anddissipation elements 14 direct stresses inwardly further into theinterior portion of the bond pattern, and the stresses are dissipated inthe interior portion of the bond pattern.

Thus, assuming the tear strength of the material being bonded is notexceeded, bond patterns of this invention provide increasedtear-resistance in a bonded composite, e.g. a bonded absorbent article,as compared to conventional bond patterns, by providing greaterdistances between adjacent bond locations for the pattern periphery,where the force-generated stress on the bond pattern is the highest. Atthe same time, the pattern is also conducive to maintaining thestructural integrity of a rotary horn and anvil system by providing arelatively constant surface area contact, and side-to-side contactbalance, between the horn and anvil.

While this invention has been described in terms of elongate bondelements, a limited number of circular bond elements can be used in thebond pattern so long as the number and placement of such circular bondelements are consistent with the principles taught herein for directingstress inwardly away from the side edges of the bond pattern.

Bond patterns of the invention typically comprise bond density of about15 percent to about 50 percent, more preferably about 20 percent toabout 40 percent. As used herein, “bond density” refers to the fractionof the bond area which is occupied by bond elements, e.g. stressreceptor elements 12, stress transfer and dissipation elements 14,and/or stress termination elements 13. Such spacing of the bond elementsfrom each other provides for distribution of stresses across unbondedportions of the bond pattern to a plurality of bond elements, albeitoptionally through adhesively bonded portions of the thin-section sheetmaterials, thereby to enhance distribution of the stress over arelatively larger number of bond elements, as well as over a relativelylarger area of the material being bonded. Such increased distribution ofthe stress operates to reduce the level of stress borne by a localizedarea of the bond pattern, thus reducing the maximum stress responseintensity experienced by the bonded materials.

Referring to FIGS. 4A and 4B, an exemplary absorbent article, namely apair of training pants 30, illustrates the use of bond pattern 10 ofFIGS. 1A and 1C, respectively. In FIGS. 4A and 4B, the training pantshave a front portion 34, a rear portion 38, and a crotch portion 36which extends from front portion 34 to rear portion 38. The absorbentarticle of FIGS. 4A and 4B comprises a liquid-impermeable outer firstthin-section element of sheet or web material as outer cover 42, aliquid-permeable body side second thin-section element of sheet or webmaterial as body side liner 44, and a liquid-absorbent core 46 disposedbetween the outer cover and the body side liner. Side seams 32 employthe illustrated bond patterns 10 to join the front and rear portions atside edges 45. Leg elastics 40 extend along leg openings 49.

Various woven and nonwoven fabrics may be used in fabricating body sideliner 44. For example, body side liner 44 can be fabricated using aperforated or reticulated film, or a meltblown or spunbonded web ofpolymeric material selected from the group consisting of polyolefinsincluding polyethylenes and polypropylenes, polyesters, and polyamides,and mixtures, copolymers, and blends of such polymeric fibers. The bodyside liner can also comprise, alone or in combination, a carded and/orbonded web composed of natural and/or synthetic fibers. Body side liner44 can also be composed of a substantially hydrophobic material whereinthe hydrophobic material is treated with a surfactant or otherwiseprocessed to impart a desired level of wettability and hydrophilicity.

Body side liner 44 can comprise, for example, a nonwoven, spunbonded,polypropylene fabric employing about 2.8-3.2 denier fibers formed into aweb having a basis weight of about 22 grams per square meter and adensity of about 0.06 grams per cubic centimeter. The fabric is thensurface treated with about 0.3 weight percent of a suitable surfactant.Body side liner 44 can also be fabricated employing a fibrous webdefining a multiplicity of randomly-spaced small openings extending froma major surface of the web into the interior of the web. The body sideliner 44 can comprise material structure such as porous foams,reticulated foams, apertured polymeric films, polymeric fibers, andnatural fibers. The body side liner can be defined in terms of length,width, and/or thickness by a multiplicity of components or layers whichcorrespond with any of the materials disclosed herein, as well as othersknown in the art.

It is generally preferred that outer cover 42 of the absorbent articlebe formed from material which is substantially impermeable to liquids. Atypical outer cover can be manufactured from a thin plastic film orother flexible liquid-impermeable material. For example, the outer covercan be formed from a film of polymeric material selected from the groupconsisting of polyolefins including polyethylenes and polypropylenes,polyesters, and polyamides, and mixtures, copolymers, and blends of suchpolymeric materials, the resulting outer cover having a thickness, forexample, of from about 0.012 millimeter to about 0.051 millimeter. Ifouter cover 42 should have a more cloth-like feeling, the outer covercan comprise a polyethylene film laminated to a surface of a nonwovenweb, such as a spunbonded web of polyolefin fibers.

For example, a polyethylene film having a thickness of about 0.015millimeter can have thermally or otherwise laminated thereto aspunbonded web of polyolefin fibers having thicknesses of from 1.5 to2.5 denier per filament, which nonwoven web has a basis weight of about24 grams per square meter. Further, outer cover 42 can be formed of awoven or nonwoven fibrous web which has been totally or partiallyconstructed or treated to impart a desired level of liquidimpermeability to selected regions which are adjacent or proximateabsorbent core 46. Still further, the outer first thin-section element42 can optionally be composed of a micro-porous material which permitsvapors to escape from absorbent core 46, through outer cover 42 and intothe ambient environment, while preventing liquid exudates from passingthrough the outer cover.

One or both of the outer cover and the body side liner can comprise afibrous web defining a multiplicity of randomly-spaced small openingsextending from a major surface of the web into the interior of the web.Polymeric material selected from the group consisting of polyolefinsincluding polyethylenes and polypropylenes, polyesters, and polyamides,and mixtures, copolymers, and blends of such polymeric materials can beused, in either film form, solid or reticulated, or in non-woven fiberforms, for one or both of body side liner 44 and outer cover 42. Also,included in definitions of the above polymeric materials are allroutine, common, and normal additives known to those skilled in the artof polymeric materials, such as for example and without limitation,processing aids, chemical stabilizers, compatibilizers where more thanone polymer is used, and fillers.

Absorbent core 46 suitably comprises a matrix of hydrophilic fibers,such as a web of cellulosic fluff, in combination with a high-absorbencymaterial commonly known as superabsorbent material. Absorbent core 46can comprise a mixture of superabsorbent hydrogel-forming particles andwood pulp fluff. In place of the wood pulp fluff, one can use syntheticpolymeric e.g. meltblown fibers or a combination of synthetic fibers andnatural fibers. The superabsorbent material can be substantiallyhomogeneously mixed with the hydrophilic fibers or can be otherwisecombined into absorbent core 46.

Absorbent core 46 can comprise a laminate of fibrous webs, optionallyincluding an uncreped through-air dried (UCTAD) cellulosic material, incombination with superabsorbent material, or other suitable means ofmaintaining a superabsorbent material in a localized area.

Absorbent core 46 can have any of a number of shapes. For example,absorbent core 46 can be rectangular, I-shaped or T-shaped. It isgenerally preferred that absorbent core 46 be narrower in the crotchportion than in the rear portion or the front portion of the absorbentarticle to the extent the absorbent article includes a waist portion,which waist portion typically has a greater width than the width at thecrotch portion.

The high-absorbency material in absorbent core 46 can be selected fromnatural, synthetic or modified natural polymers and materials. The highabsorbency material can be inorganic material, such as silica gels, ororganic compounds such as polymers, e.g. cross-linked polymers.“Superabsorbents,” which are optionally cross-linked materials, asreferred to herein, refers to any means for effectively renderingnormally water-soluble materials substantially water insoluble butswellable, whereby absorbent properties are available but the swelledmaterial is substantially immobile after absorbing water-based liquids.Such means can include, for example and without limitation, physicalentanglement, crystalline domains, covalent bonds, ionic complexes andassociations, hydrophilic associations such as hydrogen bonding, andhydrophobic associations or Van der Waals forces.

In embodiments of the invention indicative of an absorbent article ase.g. illustrated in FIGS. 4A and/or 4B, the width of the bond patternbetween the first and second side edges of the bond pattern ispreferably about 4 millimeters to about 20 millimeters, and morepreferably about 5 millimeters to about 14 millimeters. In somecontemplated embodiments of the invention, the width of the bond patternmay be up to about 4 inches.

The greater the width of the bond pattern, the more material can beincluded in the stress attenuation process, but the more material isused and, for a fixed number of bond elements, the greater the risk thatthe stress can pass through the bond pattern without being terminated.Thus, if the bond element-to-pattern area ratio is too low, the elementsare unable to cooperatively support each other whereby stress may not beadequately attenuated in the bond pattern and whereby a lack of minimumbond element density may result in layers of a bonded compositedisassociating with one another. Conversely, the less the width of thebond pattern, the less is the quantity of material used, but the greaterthe risk of not effectively spreading the stress away from the entryloci at the respective side edge and attenuating the stress. Thus,selection of a preferred specific width is a judgement to be made basedon the technical features present in a given set of circumstances,including consideration of the principles of the invention.

FIG. 5 illustrates a diaper 50 of the invention utilizing the bondpattern of FIG. 1C. Diaper 50 has a front portion 34, a rear portion 38,and a crotch portion 36 which Joins the front portion 34 and rearportion 38.

Diaper 50 comprises a liquid-impermeable outer first cover 42 as a firstthin-section element of sheet material, a liquid-permeable body-sideliner 44 as a second thin-section element, and an liquid-absorbent core46 between the outer cover and the body side liner. Additionally, sideedges are given the reference number 32, leg elastic is given thereference number 40, and the diaper ear has a reference number 48.

FIG. 6 represents a side pictorial view of bonding nip 60 such as can beused in continuous bonding processes employing, bond patterns of theinvention. Bonding nip 60 is formed between two rotating rolls 62A, 62B.Rolls 62A, 62B can be mounted at any angular orientation, each withrespect to the other, so long as energy can be effectively transmittedfrom at least one of the rolls to the material being worked in nip 60.In FIG. 6, rolls 62A, 62B are mounted such that roll 62A is positionedvertically over roll 62B. To create the bond pattern of the invention, afirst web of sheet material 64 and a second web of sheet material 66 arefed from left to right in FIG. 6 as indicated by arrows 65, 67, and areurged toward each other in face-to-face relationship, in the bonding nip60 of the machine shown in FIG. 6, to form an array of separate,distinct, and spaced elongate bond elements affixing the first andsecond thin-section sheet materials to each other.

The bond elements described herein and illustrated in the drawings areformed by, among other steps, pressing e.g. webs 64 and 66 against eachother in nip 60 in order to activate a desired form of adhesion.Typically, one of the rolls, e.g. roll 62A, has a generally smooth outercircumferential surface while the other roll, e.g. roll 62B, bears apattern of raised bonding protrusions, also called lands, correspondingin design and location to the bond pattern reflected in e.g. FIGS. 1A,1B, and 1C. While the outer surface of e.g. roll 62A can bearindentations complementing the protrusions, such is not preferred. Aswebs 64, 66 pass through the nip, rolls 62A, 62B in combination applypressure to the webs at locations on the webs corresponding to therespective protrusions, thereby activating the adhesive response at e.g.bond elements 12, 13, and 14.

The protrusions, which are shaped like respective bond elements, extendfrom a base surface on the outer circumference of roll 62B. Theprotrusions terminate at distal land surfaces which are responsible forcreating the respective bond elements. Typical such protrusions can be,for example, up to approximately 0.10 inch in height, and up to about0.06 inch in width. Height is defined as the dimension of the protrusionfrom the base circumferential surface of the roll to the distal tip, orland, which actually interfaces with e.g. the web material in whichbonds are being formed. The sides of the protrusions typically extendfrom the base circumferential surface of the roll at angles of, forexample, about 5 degrees to about 60 degrees, more preferably, about 10degrees to about 50 degrees, to an angle perpendicular to the basecircumferential surface at the respective locus on the surface of theanvil roll.

The bond pattern, as well as the individual bond elements, can beactivated by a variety of methods including but not limited to applyingpressure, thermal energy and pressure, or ultrasonic-frequency energyand pressure, to the workpiece in bonding nip 60. The workpiece definedfor this illustration can include one or more of web 64, web 66, and theresultant bonded composite 68. Where ultrasonic energy is employed, thee.g. anvil roll 62B is properly sized, as known in the art, to notdeleteriously interfere with the resonant frequency of the ultrasonichorn.

In the embodiment illustrated in e.g. one or more of FIGS. 1A-1C and2A-2D, the bond pattern created by the process described and illustratedin FIG. 6 can join e.g. superposed webs at locations generallycorresponding to the ultimate locations of side seams 32 in the finishedabsorbent article. As stated previously, such article typicallycomprises an assemblage of two or more layers or partial layers ofdifferent materials or can comprise two or more layers of substantiallythe same material, optionally along with other elements. Typical suchmaterial is a woven or non-woven fabric, or a polymer film.

As illustrated in FIG. 5, an absorbent article precursor, commonlyreferred to in the art as a work piece, can be defined as part of acontinuously processed, continuous length, composite web of materials.As a work piece is defined, a bond pattern can be formed e.g. at sideseams 32 either before or after the absorbent article is severed fromthe web, either as a fully finished or partially finished absorbentarticle.

While FIG. 6 shows only one method of implementing the bond pattern toform a bonded composite, other processes are contemplated such ascreating the bond pattern using a plunge or press horn, or any otherprocess capable of creating the bond pattern using e.g. pressure,thermal energy, or ultrasonic energy, in combination with adhesive.

While it is earlier suggested to pass the sheet materials through aseparate nip between adhesive applicator 70 and nip 60, adhesion betweenthe two sheet materials, in the stippled adhesive bonded areas 94 can,in the alternative, be developed in a separate bonding step e.g. at abonding nip after the webs 64, 66 pass through nip 60. In someembodiments, nip 60 operates to develop both the bond elements 12, 13,14, and adhesive bonds activated by the adherent material.

Additionally, the materials listed as possible materials capable ofcomprising an outer cover and a body side liner, as described inconnection with FIGS. 4A and 4B are exemplary and preferred materialsfor use in fabricating useful products according to the invention.

Those skilled in the art will now see that certain modifications can bemade to the apparatus and methods herein disclosed with respect to theillustrated embodiments, without departing from the spirit of theinstant invention. And while the invention has been described above withrespect to the preferred embodiments, it will be understood that theinvention is adapted to numerous rearrangements, modifications, andalterations, and all such arrangements, modifications, and alterationsare intended to be within the scope of the appended claims.

To the extent the following claims use means plus function language, itis not meant to include there, or in the instant specification, anythingnot structurally equivalent to what is shown in the embodimentsdisclosed in the specification.

1. A method of bonding a first thin section element and a secondthin-section element to each other, the method comprising: (a) applyingan adherent material to at least one of the first and secondthin-section elements over at least part of an area of the respectivethin-section material which is to be bonded; (b) bringing the first andsecond thin-section elements together, including at the area to bebonded; and (c) applying force urging the first and second thin-sectionelements into bonding contact with each other including at the area tobe bonded, and applying one of thermal energy or ultrasonic frequencyenergy to at least one of the first and second thin-section elements inthe area to be bonded, thereby forming an array of elongate bondelements and activating the adherent material proximate and generallyabout ones of the bone elements, the array of elongate bond elements, incombination with the activated adherent material, comprising a bondpattern having a pattern length, a pattern width represented by firstand second side edges of the bond pattern, and a central longitudinalaxis extending through an interior portion of the bond pattern, the sideedges of the bond pattern, and a corresponding bond pattern area betweensuch side edges, being defined generally by these areas of therespective thin-section elements which participate in absorbing anddissipating, by operation of the bond pattern, stresses received intothe bond pattern, the bond pattern being arranged and configured suchthat a side stress imposed from outside said bond pattern ispreferentially directed away from the respective side edge and inwardlyinto said bond pattern, and is substantially dissipated on the interiorportion of the bond pattern.
 2. A process as in claim 1 comprisingselecting, as at least one of the first thin-section element and thesecond thin-section element, a thin section element which comprisespolymeric material selected from the group consisting of polyolefinsincluding polyethylenes and polypropylenes, polyesters, and polyamides,and copolymers, mixtures, and blends of such polymeric materials.
 3. Aprocess as in claim 1 comprising selecting, as at least one of the firstthin-section element and the second thin-section element, a thin sectionelement which comprises a fibrous web defining a multiplicity ofrandomly spaced small openings extending from a major surface of the webinto the interior of the web.